WeichenXu123 commented on a change in pull request #24734:
[SPARK-27870][SQL][PySpark] Flush each batch for pandas UDF (for improving
pandas UDFs pipeline)
URL: https://github.com/apache/spark/pull/24734#discussion_r288377915
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/python/ArrowEvalPythonExec.scala
##########
@@ -86,28 +86,11 @@ case class ArrowEvalPythonExec(udfs: Seq[PythonUDF],
resultAttrs: Seq[Attribute]
sessionLocalTimeZone,
pythonRunnerConf).compute(batchIter, context.partitionId(), context)
- new Iterator[InternalRow] {
-
- private var currentIter = if (columnarBatchIter.hasNext) {
- val batch = columnarBatchIter.next()
- val actualDataTypes = (0 until batch.numCols()).map(i =>
batch.column(i).dataType())
- assert(outputTypes == actualDataTypes, "Invalid schema from
pandas_udf: " +
- s"expected ${outputTypes.mkString(", ")}, got
${actualDataTypes.mkString(", ")}")
- batch.rowIterator.asScala
- } else {
- Iterator.empty
- }
-
- override def hasNext: Boolean = currentIter.hasNext || {
- if (columnarBatchIter.hasNext) {
- currentIter = columnarBatchIter.next().rowIterator.asScala
- hasNext
- } else {
- false
- }
- }
-
- override def next(): InternalRow = currentIter.next()
+ columnarBatchIter.flatMap { batch =>
+ val actualDataTypes = (0 until batch.numCols()).map(i =>
batch.column(i).dataType())
+ assert(outputTypes == actualDataTypes, "Invalid schema from pandas_udf:
" +
+ s"expected ${outputTypes.mkString(", ")}, got
${actualDataTypes.mkString(", ")}")
+ batch.rowIterator.asScala
Review comment:
Some explanation here:
The master impl has an issue,
the member "private var currentIter = ..." will be computed when create the
returned iterator. Computing the `currentIter` require to read the first
element of `columnarBatchIter`. But note that this block code being called from
`EvalPythonExec.doExecute`, we should not read iterator here, we can only
generate iterator. Reading iterator should start after the total iterator
pipeline constructed.
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